U.S. Pat. Nos. 3,612,677 and 4,058,850 show an electrophotographic copier having a transfer drum to which a copy sheet is secured. The drum brings the copy sheet into transfer relation with two or more toner images carried on an image member to transfer those images to the copy sheet in registration. This is a common transfer apparatus for modern color copiers and has been suggested for color printers. It can also be used to combine two images of the same color.
Using such an apparatus, the circumference of the drum must be larger than the smallest dimension of the largest size copy sheet to be secured to it. When a smaller copy sheet is attached to the same drum, a portion of the drum circumference is unused. This unused circumference requires a comparable space between toner images on the image bearing member. Provision of such a space on the image bearing member reduces the output of that member at any given lineal speed, and thereby the speed of the copier or printer.
Although sizes vary around the world, a common largest size is 11 by 17 inches (approximately 28.times.43 cm.), commonly called "ledger" size. In the United States the most common size is 81/2 by 11 inches (approximately 22.times.28 cm.) or "letter" size.
Electrophotographic color copiers with drum transfer apparatus of the type described commonly can accommodate ledger size images. A gripping or vacuum mechanism attaches the leading edge of the ledger size receiving sheet to the drum. If a letter size sheet is attached to the same drum in the same orientation, six inches of drum circumference must be unused. The images must be separated by that amount on the image member. Thus, the copier or printer does not operate at its optimum speed when using the smaller size. Unfortunately, letter size is likely to be the most common size used.